More than 10 people have died in China's commercial hub of Shanghai, according to a local health official, as the city sweltered through its highest temperatures in at least 140 years.

Much of China is in the grip of a summer heatwave, and the China Meteorological Association has issued a warning for several eastern and central provinces, saying that temperatures could reach 41 degrees Celsius on Wednesday.

Tuesday marked the eighth consecutive day of temperatures above 38 degrees in Shanghai, the official Xinhua news agency reported, citing the local weather bureau.

The temperature reached 40.6 degrees last Friday, topping a previous high of 40.2 degrees in 1934 and the highest temperature since records began in 1873, Xinhua said.

Leng Guangming, a spokesman at the Shanghai Municipal Centre for Disease Control and Prevention, said there had been at least 10 victims of heat stroke in the city.

City forecasters said temperatures were "rising rapidly" and could reach a sweltering 40 degrees in People's Square on Wednesday.

Experts cited by Xinhua attributed the record-breaking heatwave to a subtropical high-pressure system and a lack of rain.

Residents of Shanghai are reportedly sheltering from the heat in air-conditioned shops or subways, and cooling off in swimming pools and rivers.

Footage of a slice of pork cooked through in 10 minutes on an outdoor stone slab, taken by a Shanghai TV station and posted online, went viral.

"It turns out that the only difference between me and roast meat is a pinch of cumin," joked one user of the Twitter-like microblog, Sina Weibo.